High current electrical lead

ABSTRACT

An electrical lead has insulators imbedded in an inner conductor rod to form an annulus between the rod and a surrounding outer sheath. This annular space is filled with gas which conducts heat and prevents electrical leakage.

THERMIONIC- CONVERTOR United States Patent 1191 1111 2 Kaufman et al.June ll 19% 54 men CURRENT ELECTRICAL LEAD 2,754,349 7/1956 Werner174/28 [751 Warner Kaufman, Broadview 5333133; 5/1338 53553223111113:J...Y.f1%/i Hlgllts; Roland Breltwlesh 3,542,938 11/1970 Graneau 174/221Fal e ark, both of Ohio 3,585,27l 6/l97l Reynolds 174/15 c [73]Assignee: VEB Filmiabrik Wolfen, Wolfen,

Germany Primary Examiner-J. D. Miller 22 pl d: l 19 1972 AssistantExaminer-Harry E. Moose, Jr. 1 16 y Attorney, Agent, or Firn1l l. T.Musial; G. E. Shook; PP'- N01 1 2 J. R. Manning [52] US. Cl 1174/15 1C,174/28, 174/111,

310/4 R [57] ABSTRACT [51] Int. Cl. Hllllb 9/04 An electricaneadhasinsmatorsimbeddedin aninner [58] held of conductor rod to form anannulus between the rod and a surrounding outer sheath. This annularspace is filled with gas which conducts heat and prevents elec- [56]References Cited meal leakage.

UNITED STATES PATENTS 2,282,004 5/1942 Scott et al 174/20 6 Claims, 1Drawing Figure HIGH CNT ELECCAL LEAD ORIGIN OF THE INVENTION Theinvention described herein was made by employees of the United StatesGovernment and may be manufactured and used by or for the Government forgovernmental purposes without the payment of any royalities thereon ortherefor.

BACKGROUND OF THE INVENTION This invention is concerned with an improvedelectrical lead for use in a high gamma flux. The lead is particularlyuseful with thermionic converters in nuclear reactors.

Thermionic converters operate in high gamma flux locations of nuclearreactors. Current is removed from such thermionic converters throughelectrical leads.

Conditions imposed upon the conductors in these leads are more severethan those for conductors of other test devices operating in a nuclearenvironment. Conductors used in nuclear tests applications have beeninsulated with swaged magnesia or alumina housed in stainless steeltubes.

Electrical leakage at high current levels is probable with swaged leadsdue to impurities in the swaged material. Heat flux into the conductorfrom the hot test piece results in a large expansion of the longconductor. The swaged lead expands mostly at the hot end thus imposing aforce on delicate components of the device under test.

. SUMMARY or THE INVENTION These problems have been solved by anelectrical lead constructed in accordance with the invention. Insulatingsapphire balls imbedded at spaced distances along an inner conductor rodform a gas annulus between the rod and a surrounding outer sheath ofstainless steel tubing. The hot end of the rod is fixed'in a cermetinsulator. The annular space between the rod and the tube is filled withan inert gas which conducts heat to the stainless steel tube andsurrounding water while preventing electrical leakage.

OBJECTS OF THE INVENTION It is, therefore, an object of the presentinvention to provide a coaxial conductor in which electrical currentleakage is minimized.

Another object of the invention is to provide an improved electricallead for use in a high gamma flux location in a nuclear reactor.

Another object of the invention is to provide an improved coaxialconductor which utilizes insulating balls imbedded in the conductor toform a gas annulus.

These and other objects of the invention will be apparent from thedrawing and specification which follow wherein like numerals are usedthroughout to identify like parts.

DESCRIPTION OF THE DRAWING The drawing is a cross-sectional view of animproved coaxial lead constructed in accordance with the presentinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawingthere is shown an electrical lead assembly 10. This assembly is used toconduct current from a thermionic converter 12 which is capable ofproducing a very high current.

The thermionic converter I2 is mounted in a nuclear reactor and operatesin a high gamma flux area l4 which may be near the reactor core. Thishigh gamma flux area 14 is surrounded by an inner wall 116 forming ahousing in the reactor. An outer wall T8 is spaced from the inner wall116 to form a container that is filled with water 20 for shielding andcooling.

The electrical lead assembly 110 is utilized to conduct high electricalcurrents from the thermionic converter 12 through the water filledcontainer. The lead assembly 110 has a sheath 22 that that is mounted inthe outer wall 18 and extends toward the inner wall 16. The sheath 22comprises a stainless steel tube. By way of example, a stainless steeltube of 0.250 inch outside diameter and 0.014 inch wall thickness with alength of 60 inches has been satisfactory for the sheath 22 in a typicalinstallation.

An electrically conducting rod 24 extends axially through the sheath 22and passes through a suitable aperture in the outer wall 18. Aluminum ispreferred for the rod 24 because of its low susceptibility to nuclearradiation heating. However, it is contemplated that a copper rod may beused in certain applications. By way of example, an aluminum rod 0.187inch in diameter by 62 inches long was inserted in the aforementionedstainless steel tube. Such a rod was satisfactory for its intended use.

Spaced insulators 26 engage the rod 24 and conduct the inner surface ofthe sheath 22. These insulators 26 maintain the rod 24 out of contactwith the sheath. In sulators 26 in the form of sapphire balls have beensatisfactory. The aforementioned aluminum rod was provided with three0.062 inch diameter holes which were drilled 0.045 inch deep and 120apart at one inch intervals. Sapphire balls of 0.062 inch diameter wereinserted with a light press fit into these holes. The rod was theninserted into the stainless steel tube to form the lead assembly 110.

An electrical conductor 2% which extends from the thermionic converter12 is rigidly secured to the end of the rod 24 adjacent the inner wall16. An insulator 30 surrounds the connected ends of the conductor 24 and28. The insulator 30 forms a rigid support for these two conductors. Acermet material has been satisfactory for the insulator 30.

A bracket 32 rigidly mounts the insulator 30 in the inner wall 16. Thebracket 32 further rigidly mounts the end of the sheath 22 onto theinner wall 16.

As seen in the drawing the ends of the sheath 22 and rigid conductor 24adjacent the inner wall 16 are both rigidly supported. The conductor 24is free to expand axially along the sheath 22 away from the insulator30. Thus there is no load placed on the cermet insulator 30.

The annulus between the rod 24 and the sheath 22 is first evacuated andthen filled to about 60 millimeters of mercury inert gas pressure.Helium or argon is satisfactory for this purpose. Heat transmitted alongthe conductor rod 24 from the thermionic converter I2 is dissipatedthrough this gas and the sheath tube 22 to a water 20. No electricalcurrent leakage is encountered because the annulus is first evacuatedand then filled with inert gas of high purity.

While the preferred embodiment of the invention has been known anddescribed it will be appreciated that ial conductor.

What is claimed is: 1. An electrical lead for conducting a high currentfrom a thermionic converter operating in a high gamma flux area in anuclear reactor that is enclosed in a water filled container comprisinga tubular sheath extending through said container whereby the watertherein cools the same,

an electrically conducting rod extending axially through said sheath,the outer surface of said rod being spaced from the inner surface ofsaid sheath to form an annulus,

a low molecular weight inert gas of high purity selected from the groupconsisting of helium and argon under a pressure of about 60 millimetersof mercury contained in said annulus to conduct heat from said rod tosaid water cooled sheath and prevent electrical current leakage,

a plurality of spaced insulators in said annulus for maintaining saidrod out of engagement with said sheath, and

a rigid insulator mounted on the end of said sheath and said rodadjacent to said nuclear reactor, said rod being free to expand axiallywithin said sheath along said spaced insulators away from said rigidinsulator and said nuclear reactor.

2. An electrical lead as claimed in claim 1 wherein the electricallyconducting rod is of a material selected from the group consisting ofaluminum and copper.

3. An electrical lead as claimed in claim 1 wherein the spacedinsulators comprise solid spheres of an insulating material.

4. An electrical lead as claimed in claim 3 wherein the solid spherescomprise sapphire balls, said rod being provided with a plurality ofspaced recesses for receiving said balls.

5. An electrical lead as claimed in claim 1 wherein the sheath comprisesa stainless steel tube.

6. An electrical lead as claimed in claim 1 wherein the rigid insulatorcomprises a cermet material.

Phtent No. arem-62 mm Jaw 280 1974 Inventor (s W. B. Kaufman and RBreitwiwer It V is certified that error appears in the above-identifiedpatent and that said Letters Patent are hereby corrected as shown below:

On the time page after {'73} Assignw:

Can1 VEB FHMFABRXK WOLFEQ wulfm Germany" and insert The United States ofAmerica as represented by I the Administmtar of the National Ar0nauticsand Space Adminis'trat:ion Washington D0 Co Signed and sealed thig ZZmflday 0f October 1974,

(SEAL) MCCOYDMO Gmsom JR, co VARSI-IALL DN Awe-stung Ufficmr Cissimer @fPatents s 10439 FORM P0 10 USCOMM-DC 60376-P69 1 Us. GDVERNMENT PRINTINGOFFICE I |969 0-366-334 Patent No. $821,462 D t d June 28,, 1974Inventor (s) Wa B. Kaufman and R. Breitwieser It is certified that errorappears in the above-identified patent and that said Letters Patent arehereby corrected as shown belaw:

On the title page after [73} Assignee:

Cancel V'EB FZIMFABRIK WGLFEN Wolfen Germany" and insert The UnitedStates of America, 215 represented by the Adminis'hmtor of the NationalAeronautics am Space Administration Washing-ton Da Cu Signed and sealedthia 22nd day 0f Octuber 191M a (SEAL) McCOY M GIBSON JR. c MARSHALL DNAttestmg Officer Camissioner 0f Patents 4050 10-69 FORM PO USCOMM-DCeoa7e.|=e9

U.5 GOVERNMENT HUNTING UFFICE I 959 O355-334

1. An electrical lead for conducting a high current from a thermionicconverter operating in a high gamma flux area in a nuclear reactor thatis enclosed in a water filled container comprising a tubular sheathextending through said container whereby the water therein cools thesame, an electrically conducting rod extending axially through saidsheath, the outer surface of said rod being spaced from the innersurface of said sheath to form an annulus, a low molecular weight inertgas of high purity selected from the group consisting of helium andargon under a pressure of about 60 millimeters of mercury contained insaid annulus to conduct heat from said rod to said water cooled sheathand prevent electrical current leakage, a plurality of spaced insulatorsin said annulus for maintaining said rod out of engagement with saidsheath, and a rigid insulator mounted on the end of said sheath and saidrod adjacent to said nuclear reactor, said rod being free to expandaxially within said sheath along said spaced insulators away from saidrigid insulator and said nuclear reactor.
 2. An electrical lead asclaimed in claim 1 wherein the electrically conducting rod is of amaterial selected from the group consisting of aluminum and copper. 3.An electrical lead as claimed in claim 1 wherein the spaced insulatorscomprise solid spheres of an insulating material.
 4. An electrical leadas claimed in claim 3 wherein the solid spheres comprise sapphire balls,said rod being provided with a plurality of spaced recesses forreceiving said balls.
 5. An electrical lead as claimed in claim 1wherein the sheath comprises a stainless steel tube.
 6. An electricallead as claimed in claim 1 wherein the rigid insulator comprises acermet material.